The invention relates to a tractor feed device for paper webs, having two tractors per paper web, which are journalled on two associated shafts and which can be driven by at least one shaft. Each tractor comprises an endless transport chain with pins and deflectable retaining flaps on their longitudinal sides, the paper web being fed by one longitudinal side of the associated tractors to the printing backing around which it is guided after which it is discharged along the other longitudinal side of the associated tractors. A pivotable guide piece is arranged on the end face of the associated tractors which faces the printing backing, to engage paper web upstream of the printing backing, viewed in the transport direction.
A transport device of this kind is known from German Offenlegungsschrift No. 20 62 806. Because the paper web is guided on the tractor on both sides, proper guiding through 180.degree. about a roller used as the printing backing is achieved. Because the paper web can expand and shrink in accordance with the air humidity, the tractor comprises a pivotable guide piece which ensures that the paper always contacts the printing roller with approximately the same tension.
During the transport and the threading of paper webs, notably in the printing device of an accounting machine, however, problems are encountered in that on the one hand the introduction into the lower or supply side of the tractors is difficult and in that on the other hand, in the case of multi-layer paper webs, the inner webs form an increasingly larger wave in front of (upstream of) the printing roller which disturbs the so-called crimp lock adhesion that fastens the individual webs together along their perforated edge zones.
However, once the adhesion has been disturbed, the webs shift with respect to each other to such an extent that the transport perforations of the individual paper layers no longer register and the pins of the endless chain cannot properly penetrate the perforations any longer. Smooth guiding of the paper webs is then no longer possible.